The pressure in a semiconductor processing chamber may be controlled by varying the rate at which process gases are exhausted from the chamber by a vacuum pumping arrangement. Different process gases are used in different respective semiconductor processing methods and for each gas, there is a desired relationship between chamber pressure and flow rate through the chamber. Therefore, for each gas, chamber pressure must be accurately controlled during semiconductor processing.
Various arrangements have been proposed for controlling the pressure in the semiconductor process chamber. In one such arrangement, a throttle valve is provided between the outlet of the semiconductor processing chamber and the inlet of the pumping arrangement. Such throttle valves are relatively large and expensive, and can be the cause of contamination in the chamber resulting in lower yield of semiconductor products. Regular cleaning of the valve is required which is inconvenient since this may require stopping the production process and opening the chamber to clean the system.
It is an object of the present invention to solve these and other problems.